Role of osteoprotegerin/receptor activator of nuclear factor kappa B/receptor activator of nuclear factor kappa B ligand axis in nonalcoholic fatty liver disease

Concomitantly with the increase in the prevalences of overweight/obesity, nonalcoholic fatty liver disease(NAFLD) has worldwide become the main cause of chronic liver disease in both adults and children. Patients with fatty liver display features of metabolic syndrome(Met S), like insulin resistance(IR), glucose intolerance, hypertension and dyslipidemia. Recently, epidemiological studies have linked obesity, Met S, and NAFLD to decreased bone mineral density and osteoporosis, highlighting an intricate interplay among bone, adipose tissue, and liver. Osteoprotegerin(OPG), an important symbol of the receptor activator of nuclear factor-B ligand/receptor activator of nuclear factor kappa B/OPG system activation, typically considered for its role in bone metabolism, may also play critical roles in the initiation and perpetuation of obesityrelated comorbidities. Clinical data have indicated that OPG concentrations are associated with hypertension, left ventricular hypertrophy, vascular calcification, endothelial dysfunction, and severity of liver damage in chronic hepatitis C. Nonetheless, the relationship between circulating OPG and IR as a key feature of Met S as well as between OPG and NAFLD remains uncertain. Thus, the aims of the present review are to provide the existent knowledge on these associations and to discuss briefly the underlying mechanisms linking OPG and NAFLD.

RANK-ligand and osteoprotegerin as biomarkers in the differentiation between periprosthetic joint infection and aseptic prosthesis loosening

AIM To assess serum levels of RANK-ligand(RANKL) and osteoprotegerin(OPG) as biomarkers for periprosthetic joint infection(PJI) and compare their accuracy with standard tests.METHODS One hundred and twenty patients presenting with a painful total knee or hip arthroplasty with indication for surgical revision were included in this prospective clinical trial. Based on standard diagnostics(joint aspirate, microbiological, and histological samples) and Musculoskeletal Infection Society consensus classification,patients were categorized into PJI, aseptic loosening,and control groups. Implant loosening was assessed radiographically and intraoperatively. Preoperative serum samples were collected and analyzed for RANKL, OPG, calcium, phosphate, alkaline phosphatase(AP), and the bone-specific subform of AP(b AP). Statistical analysis was carried out, testing for significant differences between the three groups and between stable and loose implants. RESULTS All three groups were identical in regards to age, gender, and joint distribution. No statistically significant differences in the serum concentration of RANKL(P = 0.16) and OPG(P = 0.45) were found between aseptic loosening and PJI, with a trend towards lower RANKL concentrations and higher OPG concentrations in the PJI group. The RANKL/OPG ratio was significant for the comparison between PJI and non-PJI(P = 0.005). A ratio > 60 ruled out PJI in all cases(specificity: 100%, 95%CI: 89, 11% to 100.0%) but only 30% of non-PJI patients crossed this threshold. The positive predictive value remained poor at any cut-off. In the differentiation between stable and loose implants, none of the parameters measured(calcium, phosphate, AP, and b AP) showed a significant difference, and only AP and b AP measurements showed a tendency towards higher values in the loosened group(with P = 0.09 for AP and P = 0.19 for b AP). CONCLUSION Lower RANKL and higher OPG concentrations could be detected in PJI, without statistical significance.

Receptor activator of nuclear factorκB ligand/osteoprotegerin axis and vascular calcifications in patients with chronic kidney disease

Vascular calcifications are commonly observed in patients with chronic kidney disease （CKD） and contri-bute to the excessive cardiovascular morbidity and mortality rates observed in these patients populations. Although the pathogenetic mechanisms are not yet fully elucidated, recent evidence suggests a link between bone metabolism and the development and progression of vascular calcifications. Moreover, accumulating data indicate that receptor activator of nuclear factor κB ligand/osteoprotegerin axis which plays essential roles in the regulation of bone metabolism is also involved in extra-osseous bone formation. Further studies are required to establish the prognostic significance of the above biomarkers as predictors of the presence and severity of vascular calcifications in CKD patients and of cardiovascular morbidity and mortality. Moreover, randomized clinical trials are needed to clarify whether inhibition of osteoclast activity will protect from vascular calcifcations.

Alendronate affects osteoprotegerin/receptor of activator of nuclear factor κB-ligand expression in human marrow stroma cells in vitro

Objective To evaluate the effect of alendronate on osteoprotegerin(OPG)and receptor of activator of nuclear factor κB-ligand(RANKL)expression in human marrow stroma cells(hMSCs)in vitro.Methods hMSCs were isolated from human marrow,cultured in vitro,and randomly divided into two groups:alendronate group,hMSCs culture fluid containing 1×10-7mol/L alendronate;control group,no special treatment but culturing hMSCs in DMEM.Two weeks after treatment,the expressions of OPG and RANKL were evaluated by RT-PCR and Western blot.Results hMSCs became uniform spindle-shaped fibroblasts.As cells proliferated,they formed colonies and showed whirlpool arrangement.After one week’s treatment,hMSCs in alendronate group had reduced processes and gradually showed disc shape,which did not happen in control group but kept fibroblast shape and just increased in density.In RT-PCR,the ratio of OPG/RANKL in alendronate group and control group was 8.77±1.16 and 4.58±1.27,respectively.In Western blot,the ratio of OPG/RANKL in alendronate group and control group was 2.58±0.47 and 1.52±0.32,respectively.The ratio of OPG/RANKL was higher in alendronate group than in control group(P<0.01).Conclusion Alendronate enhances OPG expression and inhibits RANKL expression of hMSCs in vitro.

Influence of baicalin on the expression of receptor activator of nuclear factor-κB ligand and osteoprotegerin in human periodontal ligament cells

Objective To study the effect of baicalin on the expression of receptor activator of nuclear factor-κB ligand(RANKL)and osteoprotegerin(OPG)in cultured human periodontal ligament(HPDL)cells.Methods Small interfering RNA(siRNA)eukaryotic expression vector targeted transforming growth factor βⅡ receptor(TGF-β RⅡ)was constructed and transfected into T cells.HPDL cells with T cells transfected with siRNA or not were placed in the culture medium that had been added with lipopolysaccharide(LPS)and baicalin.The obtained solution was divided into six groups according to the components(group Ⅰ:HPDL cells+LPS+T cells transfected with siRNA1+baicalin;group Ⅱ:HPDL cells+LPS+T cells transfected with siRNA1;group Ⅲ:HPDL cells+LPS+T cells+baicalin;group Ⅳ:HPDL cells+LPS+T cells;group Ⅴ:HPDL cells+baicalin;group Ⅵ:HPDL cells)and was cultured for 48 hours.RT-PCR was used to observe the effect of baicalin on the expression of OPG-RANKL in HPDL cells.Results The ratio of RANKL/OPG in group Ⅰ was lower than that in group Ⅱ(P<0.01)and higher than that in group Ⅲ(P<0.01);The ratio of RANKL/OPG in group Ⅲ was lower than that in group Ⅳ(P<0.01);the ratio of RANKL/OPG in group Ⅳ was higher than that in group Ⅵ(P<0.01);the ratio of RANKL/OPG in group Ⅴ was lower than that in group Ⅵ(P<0.05).Conclusion ① Baicalin could decrease the ratio of RANKL/OPG in HPDL cells.② The TGF-β signaling transduction plays an important role in the effect of baicalin on the RANKL/OPG ratio in HPDL cells.③ Baicalin acts not only through TGF-β to regulate RANKL/OPG in HPDL cells,but also through other pathways.

Osteoprotegerin,interleukin and hepatocyte growth factor for prediction of diabetes and hypertension in the third trimester of pregnancy

BACKGROUND Gestational diabetes mellitus(GDM)raises the risk of high blood pressure and may cause a series of life-threatening complications in pregnant women.Screening and management of GDM and gestational hypertension(GH)in pregnancy helps to control and reduce these risks and prevent adverse effects on mothers and their fetuses.Currently,the majority criteria used for screening of diabetes mellitus is oral glucose tolerance tests,and blood pressure test is usually used for the screening and diagnosis of hypertension.However,these criteria might not anticipate or detect all GDM or GH cases.Therefore,new specific predictive and diagnostic tools should be evaluated for this population.This study selected three biomarkers of osteoprotegerin(OPG),interleukin(IL)and hepatocyte growth factor(HGF)for GDM and GH predication and diagnosis.AIM To explore the feasibility of changes in placental and serum OPG,IL and HGF as tools for prediction and diagnosis of diabetes and hypertension in pregnant women.METHODS From January 2018 to January 2019,44 pregnant women with GDM and GH were selected as an observation group,and 44 healthy pregnant women were selected as a control group in the same period.Serum OPG,IL and HGF were compared between the two groups.RESULTS The levels of OPG and HGF in the observation group were lower than in the control group,and the level of IL-1βwas higher in the observation group than in the control group(all P<0.05).Furthermore,OPG and HGF were negatively associated with gestational diabetes and gestational hypertension,while IL-1βwas positively associated with GDM complicated with GH(all P<0.05).CONCLUSION The evaluation of serum OPG,HGF and IL-1βlevels in patients with coexistent gestational diabetes complicated with hypertension can predict the degree of disease and play an important role in the follow-up treatment and prognosis prediction.

Integrative Analysis Confirmed the Association between Osteoprotegerin and Osteoporosis

Objective This study aimed to verify the association between osteoprotegerin gene (OPG) and its variants with osteoporosis (OP) by performing integrative analysis.Methods We used the KGG software to perform gene-based association analysis,which integrated all publicly available single-nucleotide polymorphism (SNP)-based P values and obtained an overall P value for the OPG.The significant SNPs were screened for expression quantitative trait loci (eQTLs).Meta-analysis was used to combine the associations between the variants of OPG and bone mineral density (BMD) reported in the literatures.Then we performed dual-luciferase reporter gene systems for the functional verification of the variants of OPG in vitro.Results In the gene-based association analysis,the over all P value of OPG was 6.24×10^-13 for BMD at femoral neck (FN) and 7.37×10^-17 for BMD at lumbar spine (LS),indicating the importance of OPG for OP.The publicly available eQTL database identified 5 eQTLs which exert cis-regulation effects on OPG at FN and LS.Literature searching found that rs2073617 (known as T950C) was the hot spot SNP.There were 13 relevant studies on rs2073617 besides the GEFOS-2 study identified from the PubMed.Significant differences among TT,TC and CC genotypes at FN (P= 0.047) and LS (P= 0.025) were shown by meta-analysis,demonstrating the associations between T950C polymorphism and BMD.Luciferase gene expression was significantly higher at the presence of allele C than allele T in the 293T cells (t=-9.47,P<0.01).Conclusion The integrative analysis further confirmed the importance of OPG in OP and the correlation of T950C polymorphism with BMD of OP.The strategy can be used as a reference for functional interpretation of other disease-related genes.

Efficacy of recombinant human osteoprotegerin combined with tinidazole in the treatment of periodontitis mice and its correlation with serum RANKL and MCP-1 levels

Objective: To investigate the effect of recombinant human osteoprotegerin combined with tinidazole on mice with periodontitis and the effect on serum RANKL and MCP-1 levels. Methods: 80 SPF-cleaned mice were randomly divided into 4 groups, 20 each, model group, tinidazole group and recombinant human osteoprotegerin group were modeled by Kimura et al., and tinidazole group received tinidazole. After intragastric administration, the recombinant human osteoprotegerin group was injected with recombinant human osteoprotegerin in the periodontal pocket according to the tinidazole group. The periodontal changes of the four groups of mice were observed and recorded, and the gingival rating was performed. Epithelial tissue morphology was observed by hematoxylin-eosin (HE) staining. Serum levels of IL-4, IL-6, RANKL and MCP-1 were measured by enzyme-linked immunosorbent assay. Results:After the intervention, the model group developed severe inflammatory reactions, including redness, hemorrhage, and deep periodontal pockets. The teeth were significantly loosened. The mice in the tinidazole group and the recombinant human osteoprotegerin group recovered substantially, and the gingival rating of the recombinant human osteoprotegerin group was better than that. The tinidazole group and the model group (P<0.05). The results of HE staining showed that the model group had edema, vasodilation and a large amount of inflammatory infiltration. The epithelial structure of the mice in the tinidazole group and the recombinant human osteoprotegerin group was intact and arranged closely and orderly. After intervention, the IL-4 in the tinidazole group and the recombinant human osteoprotegerin group was significantly higher than the model group and IL-6 was significantly lower than the model group (P<0.05), and the recombinant human osteoprotegerin group IL-4 was significantly higher after the intervention. IL-6 was significantly lower in the tinidazole group than in the tinidazole group (P<0.05). After the intervention, the tinidazole group and the recombinant human osteoprotegerin group were significantly reduced, and the recombinant human osteoprotegerin group RAKNL and MCP-1 were significantly lower than the model group (P>0.05). Conclusion: Recombinant human osteoprotegerin combined with tinidazole has a better therapeutic effect on gums and teeth in mice with periodontitis, and can lower the levels of RAKNL and MCP-1 in serum, inhibit bone resorption and protect teeth.

Regulation of osteoprotegerin expression by Notch signaling in human oral squamous cell carcinoma cell line

Objective: To investigate the influence of Notch signaling on osteoprotegerin(OPG)expression in a human oral squamous cell carcinoma cell line.Methods: Activation of Notch signaling was performed by seeding cells on Jagged1 immobilized surfaces. In other experiments, a g-secretase inhibitor was added to the culture medium to inhibit intracellular Notch signaling. OPG m RNA and protein were determined by real-time PCR and ELISA, respectively. Finally, publicly available microarray database analysis was performed using connection up- or down-regulation expression analysis of microarrays software.Results: Jagged1-treatment of HSC-4 cells enhanced HES1 and HEY1 m RNA expression, confirming the intracellular activation of Notch signaling. OPG m RNA and protein levels were significantly suppressed upon Jagged1 treatment. Correspondingly, HSC-4 cells treated with a g-secretase inhibitor resulted in a significant reduction of HES1 and HEY1 m RNA levels, and a marked increase in OPG protein expression was observed.These results implied that Notch signaling regulated OPG expression in HSC-4 cells.However, Jagged1 did not alter OPG expression in another human oral squamous cell carcinoma cell line(HSC-5) or a human head and neck squamous cell carcinoma cell line(HN22).Conclusions: Notch signaling regulated OPG expression in an HSC-4 cell line and this mechanism could be cell line specific.

Increased expression of osteoprotegerin in vascular smooth muscle cells from spontaneously hypertensive rats

Background Osteoprotegerin (OPG) is a secreted protein of the tumor necrosis factor receptor family, which regulates bone mass by inhibiting osteoclast differentiation and activation. Although OPG is expressed ubiquitously and abundantly in many tissues and cell types including vascular cells, the role of OPG in other tissues is unknown.Our previous studies demonstrated that OPG was highly expressed in vascular smooth muscle cells (VSMC) and upregulated during vascular lesion formation. Methods and Results We documented, by Northern blot analysis,that the expression of OPG was more prevalent in the aorta and cultured VSMC from spontaneously hypertensive rats (SI-IR) compared to Wistar-Kyoto rats (WKY). In addition, we found that the expression of Angiotensin II (Ang II)type I receptor (AT1R) in SHR VSMC was at significantly increased levels than in WKY VSMC. Furthermore, Ang II potently induced the expression of OPG in VSMC in a time- and dose-dependent manner through the AT1R signaling pathway. Conclusions OPG expression was substantially greater in SHR VSMC, suggesting that OPG may be an important determinant of vascular remodeling in SHR.

No evidence of circulating autoantibodies against osteoprotegerin in patients with celiac disease

AIM:To investigate risk factors for low bone mineral density(BMD) in celiac disease(CD) patients,focusing on circulating autoantibodies against osteoprotegerin(OPG).METHODS:Seventy asymptomatic CD adult patients on gluten-free diet(GFD) and harbouring persistent negative CD-related serology were recruited.Conventional risk factors for osteoporosis(e.g.,age,sex,menopausal status,history of fractures,smoke,and body mass index) were checked and BMD was assessed by dual energy X ray absorptiometry.Serum calcium and parathyroid hormone(PTH) levels were evaluated.Thirty-eight patients underwent repeat duodenal biopsy.Serum samples from a selected sub-group of 30 patients,who were also typed for human leukocyte antigen(HLA) DQ2 and DQ8 haplotype,were incubatedwith homodimeric recombinant human OPG and tested by western blotting with an anti-OPG antibody after immunoprecipitation.RESULTS:Despite persistent negative CD-related serology and strict adherence to GFD,49 out of the 70(74%) patients displayed low BMD.Among these patients,13(24%) showed osteoporosis and 36(76%) osteopenia.With the exception of age,conventional risk factors for osteoporosis did not differ between patients with normal and low BMD.Circulating serum calcium and PTH levels were normal in all patients.Duodenal mucosa healing was found in 31(82%) out of 38 patients who underwent repeat duodenal biopsy with 20(64%) still displaying low BMD.The remaining 7 patients had an incomplete normalization of duodenal mucosa with 6(84%) showing low BMD.No evidence of circulating antibodies against OPG was found in the serum of 30 celiac patients who were tested for,independent of BMD,duodenal histology,and HLA status.CONCLUSION:If any,the role of circulating autoantibodies against OPG in the pathogenesis of bone derangement in patients with CD is not a major one.

Effect of Osteoprotegerin and XRCC3 Genes Polymorphisms with the Occurrence of Left Ventricular Hypertrophy in Hypertensive Patients

Background: High blood pressure is associated with adverse morphological and functional changes in the cardiovascular system, including left ventricular hypertrophy (LVH). Osteoprotegerin (OPG) is a member of the tumor necrosis factor receptor superfamily of cytokines. X-ray repair cross-complementing protein 3 (XRCC3) is involved in the repair pathway for double-strand breaks (DSBs). We assessed the association of osteoprotegerin and XRCC3 gene polymorphisms with the occurrence of left ventricular hypertrophy in hypertensive patients. Patients and methods: The study included 50 hypertensive patients: 25 with LVH (group A) and 25 without LVH (group B). All cases were subjected to complete history taking and clinical examination. ECG and echocardiography were done. LV mass was calculated to detect the presence or absence of LV hypertrophy. DNA was extracted from blood samples, and then, each DNA sample was amplified in PCRs, to detect osteoprotogrin and XRCC3 gene polymorphisms. Results: Mean age in the cases in group A is 63.12 years and in group B was 58.24 years with statistically significant difference between the two groups. The duration of the disease and SBP revealed statistically significant difference between the two groups. The LV mass index and E/A ratio revealed high statistically significant difference between the two groups. OPG sequence revealed no statistically significant difference between the two groups, but XRCC3 sequence revealed statistically significant difference. The age was a risk factor for LVH. Conclusion: Osteoprotogrin and XRCC3 genes polymorphism mutations may be associated with left ventricular hypertrophy in hypertensive patients.

Osteoprotegerin Secretion by Mevastatin via p38MAPK and NF-kB

Osteoprotegerin (OPG) is a protein produced by many cell types that has the remarkable property of inhibiting bone loss. It does this by binding to the key bone resorptive cytokine, receptor activator of NF-kB ligand (RANKL). This cytokine is produced mainly by osteoblastic cells and is instrumental in osteoclast differentiation. If the ratio of RANKL:OPG increases, bone resorption increases and results in bone loss in diseases such osteoporosis, rheumatoid arthritis and hypercalcaemia of malignancy. Hence, if drugs can be found that increase OPG, this will decrease the activity of osteoclasts and therefore bone resorption. Statins are cholesterol lowering drugs that have recently been shown to increase bone formation in rodents. It was hypothesised from this finding that this could be due to an increase in OPG production. If these commonly prescribed drugs could be used to prevent bone loss or to increase bone formation then this may prove a useful means of reducing fracture risk in patients. Treating Saos-2 osteoblast-like cells in vitro with mevastatin increased OPG production and secretion through the mevalonate pathway. A failure of geranylgeranylation of Rho and/or farnesylation of Ras proteins leads to an increase in PI-3K activation then AKT activation leading to several different signaling pathways such as MAPK’s and NF-kB. NF-kB and p38MAPK inhibitors prevented the statin stimulation of OPG but not the decrease in cell number, suggesting that statins regulate OPG secretion via PI-3K, p38MAPK and NF-kB.

黄芪补肾活血汤对芳香化酶抑制剂诱导骨质疏松模型小鼠破骨细胞活性的影响

背景:芳香化酶抑制剂尽管显著提高了激素受体阳性乳腺癌患者的临床获益,但其相关的不良事件——骨质疏松严重影响了患者的生活质量,黄芪补肾活血汤能有效预防芳香化酶抑制剂所致骨质疏松的发生,但是其作用机制尚不清楚。目的:探究黄芪补肾活血汤对芳香化酶抑制剂所致骨质疏松模型小鼠破骨细胞活性的影响及机制。方法:选取60只8周龄C57BL/6J雌性小鼠随机分为假手术组、模型组、黄芪补肾活血汤高、中、低剂量组、阳性对照组各10只,除假手术组外,其余组小鼠均切除双侧卵巢联合皮下注射来曲唑构建绝经后芳香化酶抑制剂所致骨质疏松模型,黄芪补肾活血汤高、中、低剂量组分别给予19.24,9.62,4.81 g/(kg·d)黄芪补肾活血汤进行灌胃(1次/d),阳性对照组给予阿仑膦酸钠5 mg/kg灌胃(1次/周)。给药3个月后,Micro-CT检测胫骨骨密度和骨微结构,对股骨进行苏木精-伊红染色、抗酒石酸酸性磷酸酶染色及免疫组化检测核因子κB受体活化因子配体、骨保护素蛋白表达,ELISA检测血清中Ⅰ型胶原交联羧基端肽、抗酒石酸酸性磷酸酶5b水平。结果与结论:①与假手术组相比,模型组小鼠骨密度显著下降、骨小梁形态疏松断裂、血清中Ⅰ型胶原交联羧基端肽、抗酒石酸酸性磷酸酶5b水平显著上升,表明芳香化酶抑制剂所致骨质疏松模型构建成功;②与模型组相比,黄芪补肾活血汤高、中、低剂量组和阳性对照组小鼠骨密度、骨微结构显著改善,骨小梁形态增粗致密,血清中Ⅰ型胶原交联羧基端肽、抗酒石酸酸性磷酸酶5b水平显著下降,破骨细胞数量减少,核因子κB受体活化因子配体蛋白表达下降,骨保护素蛋白表达升高。结果表明,黄芪补肾活血汤可能调控核因子κB受体活化因子配体/核因子κB受体活化因子/骨保护素信号通路抑制破骨细胞活性,改善骨小梁形态和骨微结构,提高骨密度,进而预防芳香化酶抑制剂所致骨质疏松模型的发生发展。

白藜芦醇激活细胞外信号调节激酶5信号蛋白促进小鼠MC3T3-E1细胞增殖

背景:细胞外信号调节激酶5信号蛋白对生物体的存活不可或缺,白藜芦醇能通过多种途径促进成骨细胞增殖,但其是否能通过细胞外信号调节激酶5信号蛋白调控成骨细胞功能还需进一步验证。目的:探究细胞外信号调节激酶5对MC3T3-E1细胞增殖以及相关分泌蛋白的调控作用,进一步验证白藜芦醇通过激活细胞外信号调节激酶5完成上述过程。方法:小鼠MC3T3-E1前成骨细胞分别用完全培养基、XMD8-92(细胞外信号调节激酶5抑制剂)、表皮生长因子(细胞外信号调节激酶5激活剂)和白藜芦醇单独干预及XMD8-92+表皮生长因子、白藜芦醇+XMD8-92干预后,通过Western blot检测各组细胞内细胞外信号调节激酶5、磷酸化细胞外信号调节激酶5蛋白,增殖相关蛋白Cyclin D1、CDK4、PCNA,以及成骨细胞分泌蛋白骨保护素、核因子κB受体活化因子配体的表达情况,使用细胞免疫荧光染色检测各组细胞外信号调节激酶5、骨保护素和核因子κB受体活化因子配体荧光强度,使用EdU染色检测各组细胞增殖情况。白藜芦醇干预MC3T3-E1细胞的适宜浓度及时间由细胞形态学观察和CCK-8实验确定。结果与结论:①细胞外信号调节激酶5信号蛋白的激活能有效促进MC3T3-E1细胞增殖、上调骨保护素/核因子κB受体活化因子配体比值;②白藜芦醇干预MC3T3-E1细胞的适宜浓度及时间为5μmol/L,24 h;③白藜芦醇可以激活细胞外信号调节激酶5信号蛋白,进而促进成骨细胞增殖,并上调骨保护素/核因子κB受体活化因子配体比值;④研究结果表明,白藜芦醇可以通过激活细胞外信号调节激酶5信号蛋白促进MC3T3-E1细胞增殖,并通过激活细胞外信号调节激酶5信号蛋白上调骨保护素/核因子κB受体活化因子配体比值。

Increased Expression of Receptor Activator of Nuclear Factor-κB Ligand in Osteoblasts from Adolescent Idiopathic Scoliosis Patients with Low Bone Mineral Density

Persistent generalized low bone mineral density (BMD) has been reported in patients with adolescent idiopathic scoliosis (AIS).However,the exact mechanisms and causes of the low BMD in AIS patients are largely unknown.The purpose of this study was to examine the relationship between the receptor activator of NF-κB ligand (RANKL)/osteoprotegerin (OPG) levels in osteoblasts (OBs) from AIS patients with low BMD and with comparison made between the patients and controls.Twenty AIS patients and eight age-matched controls were included in the present study.The BMD of lumbar spine and proximal femur was measured in all subjects.OBs from the cancellous bone of each subject was harvested and primarily cultured.The mRNA and protein expression of RANKL and OPG in OBs was detected by RT-PCR and Western blotting.The results showed BMD was lower in AIS patients than in controls.A significantly higher mRNA and protein expression of RANKL was observed in OBs from AIS patients,while no significant difference was found in the expression of OPG between AIS patients and controls.As a result,RANKL/OPG ratio in patients with AIS was remarkably higher than controls.Our study preliminarily demonstrated expression of RANKL was higher in OBs from AIS patients with low BMD as compared with controls,suggesting the unbalanced RANKL/OPG ratio caused by an over-expression of RANKL in OBs may be responsible for the low BMD in AIS patients.

Implication of Receptor Activator of NF-κB Ligand in Wnt/β-Catenin Pathway Promoting Osteoblast-like Cell Differentiation

Recent studies showed that activation of Wnt/β-catenin pathway promoted the differentiation of osteoblast-like cells in the arterial calcification, but its mechanism remains unknown. In this study, the hypothesis that Wnt/β-catenin pathway promotes the differentiation of osteoblast-like cells by upregulating the expression of receptor activator of NF-κB ligand (RANKL) was examined. LiCl was used to activate the Wnt/β-catenin pathway. The differentiation of osteoblast-like cells was observed by Von Kossa staining, calcium content assay, alkaline phosphatase (ALP) activity assay, and detection of osteocalcin expression. Real-time PCR was performed to detect the expression of RANKL and osteoprotegerin (OPG, the decoy receptor of RANKL) during the osteoblast-like cell differentiation. Different concentrations of OPG were added to the culture media respectively to inhibit the function of RANKL, and the change in the differentiation of osteoblast-like cells was evaluated. The results showed that when the Wnt/β-catenin pathway was activated by LiCl, the expression of RANKL was significantly in-creased, which coincided with the differentiation of osteoblast-like cells (P<0.05), and the OPG treatment could partly attenuate the promoting effect of Wnt/β-catenin pathway on the differentiation of osteoblast-like cells (P<0.05), but it failed to completely abolish such effect. It was concluded that activation of Wnt/β-catenin pathway promotes the differentiation of osteoblast-like cells by both RANKL-dependent and RANKL-independent mechanisms.

Effect of Triptolide on Expression of Receptor Activator of Nuclear Factor-κB Ligand in Rat Adjuvant Induced Arthritis

The effect of triptolide （TP） on the expression of receptor activator of nuclear factor-κB ligand （RANKL） and osteoprotegerin （OPG） was explored in rat adjuvant induced arthritis （AA）. AA was induced in Wistar rats. Arthritis rats were treated with TP and methotrexate （MTX） at the onset （day 9） of arthritis. On the peak of arthritis （day 24）, the expression of RANKL and OPG protein in the joints and RANKL mRNA in peripheral blood mononuclear cells （PBMC） was detected. TNF-α and IL-1β levels in peripheral blood were determined. Bone erosion scores were also evaluated. The results showed that bone erosion scores in TP and MTX groups were lower than in AA group （.P〈0.01） ; The expression levels of RANKL in the synovium （P〈0.01） and bone （P〈0.05）, and OPG level in synovium （P〈0.05） were lower in TP group than in AA group （P〈0.05）. In TP group, the expression levels of RANKL mRNA and TNF-α, IL-1β in PBMC were lower than in AA group （all P〈0.01）. It was concluded that TP could inhibit rat adjuvant arthritis bone erosion by suppressing the expression of RANKL.

丹参酮ⅡA调节骨关节炎小鼠骨代谢的作用机制

目的探讨丹参酮ⅡA(TanⅡA)通过介导Yes激酶相关蛋白(Yes-associated protein,YAP)、核因子-κB受体活化因子配基(receptor activator of nuclear factor-κB ligand,RANKL)/核因子κB受体活化因子(eceptor activator of nuclear factor-κB,RANK)/骨保护蛋白(osteoprotegerin,OPG)调节骨关节炎小鼠骨代谢的作用机制。方法建立骨关节炎小鼠模型,将60只小鼠随机分成假手术组、模型组、TanⅡA低剂量组和TanⅡA高剂量组,每组15只,造模成功后灌胃给药,连续4周。HE和番红O固绿染色观察软骨组织病理损伤并进行Mankin评分。酶联免疫吸附试验(enzyme-linked immunosorbent assay,ELISA)检测血清骨碱性磷酸酶(bone alkaline phosphatase,BALP)、骨钙素(osteocalcin,OC)、Ⅰ型胶原交联羧基末端肽(C-telopeptide of typeⅠcollagen,CTX)、白细胞介素(interleukin,IL)-1β、IL-6、IL-8和肿瘤坏死因子-α(tumor necrosis factor-α,TNF-α)。蛋白质印迹法(Western blotting)检测基质金属蛋白酶(matrix metalloproteinases,MMPs)、YAP、RANK、RANKL和OPG蛋白。结果TanⅡA可改善小鼠软骨组织病理变化并降低Mankin评分。与假手术组比较,模型组BALP、OC水平下降,CTX、TNF-α、IL-6、IL-1β、IL-8、MMP1、MMP3和MMP13水平升高(P<0.05)。与模型组比较,TanⅡA低剂量组、TanⅡA高剂量组BALP、OC水平升高,CTX、TNF-α、IL-6、IL-1β、IL-8、MMP1、MMP3和MMP13水平降低(P<0.05)。与假手术组比较,模型组小鼠软骨组织中YAP、OPG和RANK蛋白水平下降,RANKL蛋白水平升高(P<0.05);与模型组比较,TanⅡA 2组小鼠软骨组织中YAP、OPG和RANK蛋白水平上升,RANKL蛋白水平下降(P<0.05)。结论TanⅡA可能通过介导YAP、RANK/RANKL/OPG信号通路调控骨关节炎。